274 Reports and Proceedings. 



East Kilbride. The discovery of these species by Ure bore evidence 

 to bis close powers of observation, and in this respect be compared 

 favourably with many wbo had followed him in the path of palseon- 

 tological research. With the exception of Hibbert, who described 

 two species from the limestone of Burdiehouse, this group of fossils 

 remained imnoticed in Scotland, until the subject was taken up by 

 some of the members of the Society within the last few years ; and 

 to their very close researches the authors have been largely indebted 

 — the list now embracing upwards of fifty species. The leading 

 features of the various genera — Cytliere, Bairdia, Leper ditia, Beyri- 

 cTiia, and KirJcbya — were then sketched, and Tables exhibited, show- 

 ing their range in the Carboniferous strata of Clydesdale. An 

 examination of these Tables showed that, with a few exceptions, all 

 the species had been found in the Lower Limestone Series of that 

 district. Several of them do not extend beyond the limits of that 

 division, though the majority range iato the Upper Limestone ; and 

 only four are known to occur in the shales and ironstones of the 

 Upper Coal Series. It was interesting thus to notice this group of 

 species in their life-history in the Carboniferous era. Their appear- 

 ance and dying out was not a regular unbroken process ; nor did 

 they all appear to have ever existed in one area at any one period of 

 time, notwithstanding their presence in nearly all the beds of one 

 series. For example, in a limestone or calcareous shale, with marine 

 fossils, certain species of the above-named genera were generally 

 found. Above these strata might be either arenaceous rocks or alum- 

 shales, in which these sjoecies were absent. The next stratum might 

 be one of those termed "freshwater limestone," containing Fish 

 remains, Spirorhis, and vegetable fossils. The Entomostraca in this 

 bed might be three or four Cyiheres, of species different from those in 

 the first-named deposits. Higher in the series occurs another bed of 

 shale, containing marine fossils, and with them all, or most of the 

 Bairdice, some JBeyricTim, that had occurred before, with, perhaps, 

 one or two forms to take the place of others that had not returned. 

 The species all vanish again with the second bed of shale ; and 

 probably the next occurrence of Entomostraca would be considerably 

 higher up, when one of the Cytheres of the " freshwater limestone " 

 would return, and abound alone in a single thin stratum. This 

 interchange of species continued time after time ; not, perhaps, 

 always to the same extent, but always with some variation in the 

 distribution. Nevertheless, there is considerable persistence in many 

 of the species that return at different intervals — the same groups of 

 species appearing and re-appearing many times without any essential 

 change in their constitution. They always, moreover, re-appeared 

 under exactly the same condition. Several examples of this were 

 quoted. The authors concluded their valuable communication by 

 discussing the physical conditions which had prevailed during the 

 deposition of the Carboniferous series of rocks in Scotland. 



To illustrate the paper, Mr. John Young exhibited his interesting 

 collection of mounted specimens of Entomostraca from the Carboni- 

 ferous Limestones and Shales of the West of Scotland. 



